A lot of people seem think I am old school because I still sketch out my ideas on paper before I comp them up on my computer so you always see me carrying around a velum pad and sharpie. I also think there can be a lot of value in turning those low fidelity sketches of interface ideas into quick and dirty prototypes so you can see if your idea will hold up once you starting using it. I recently also switched from my velum pad to index cards that already have an iPhone silhouette printed on them to save me the trouble of always having to draw that outline over and over again. I use these cards from Chop Shop which are just $7.50 for 100 and work great. But I was having trouble finding an easy way to get those sketching into a quick working prototype until I found a new iPhone app called POP – Prototyping on Paper. This app lets you easily snap photos of your sketches, define hot spots and then instantly have a usable and sharable prototype. Designers need to be doing a lot more of this type of rapid prototyping when it comes to mobile because you ideas never really work out the way you think they will once you have it on a device and in your hand. You can download the iPhone app here.